Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This original study investigated organic fertilizer lead transfer to vegetables in tropical mountain agroecosystems by tracking how aerobic transformation of poultry litter alters lead (Pb) speciation, adsorption mechanisms, water solubility, and subsequent transfer into edible plant parts. The authors followed poultry litter for 120 days, characterized humic fractions (HA/FA) by FTIR and solid-state 13C-NMR, quantified Pb fractions via modified BCR sequential extraction, modeled adsorption isotherms, and related organic matter structures to Pb bioavailability and plant contamination profiles for regionally grown vegetables.
Who was studied?
The research focused on poultry litter used as organic fertilizer in Brazilian tropical mountain vegetable systems and on commonly consumed crops, broccoli, kale (cabbage), cauliflower, tomato, parsley, and lettuce cultivated under local management that applies high poultry-litter rates. While no human participants were enrolled, the work integrates prior field datasets on Pb levels in edible tissues from those crops and compares them to ANVISA and FAO/WHO maximum limits, providing a population-relevant exposure lens because these vegetables enter the general commercial supply.
Most important findings
| Critical point | Details |
|---|---|
| Pb concentrates during aerobic transformation | Total Pb in poultry litter rose from 9.42 mg kg⁻¹ at day 0 to a 199.18% enrichment by day 120 due to mass loss during mineralization, increasing the absolute pool potentially mobilizable to crops. |
| Water-soluble Pb fraction expands markedly | The water-soluble fraction (F1) increased from 3.17% to 15.30% over 120 days, corresponding to an absolute rise from 0.30 to 4.28 mg kg⁻¹, despite alkaline pH (≈8.3→10.3), signaling formation of stable soluble complexes that resist precipitation. |
| Labile, hydrophilic OM structures drive Pb solubility | PCA linked soluble Pb to O-alkyl (CAlk–O) and di-O-alkyl (CAlk–di–O) carbons (polysaccharide-like, hydrophilic, labile) that persist in HA/FA through humification, maintaining Pb in bioavailable forms. |
| Adsorption capacity declines with transformation | Linear isotherm Kd fell from 1135.50 (fresh) to 87.49 (day 120), evidencing weaker sorption and greater mobility as litter humifies and surfaces become smoother/less heterogeneous. |
| Shift from inner-sphere to more outer-sphere binding | Although specific (inner-sphere) sorption remained >90%, nonspecific (outer-sphere) sorption increased from 0.37% to 4.88% with transformation, making Pb more readily exchangeable and mobile under field conditions. |
| Vegetables frequently exceed Pb limits when fertilized with fresh litter | Percent of samples above limits: broccoli 100%, kale 91.78%, tomato 80.00%, parsley 65.96%, lettuce 49.19%, cauliflower 32.88%; means for all crops exceeded ANVISA/FAO limits, highlighting high consumer-exposure risk. |
| Mechanistic coherence across methods | SEM showed granular deposits consistent with Pb complexation on fresh litter surfaces; PCA and isotherms corroborated that less-humified, aliphatic, oxygenated structures favor Pb affinity yet also sustain soluble complexes that plants can take up. |
Key implications
For regulators, organic fertilizer lead transfer to vegetables indicates that untreated or freshly stored poultry litter can elevate dietary Pb exposure, necessitating explicit HTMC thresholds for input materials and finished produce. Certification should require verified Pb limits in litter, proof of treatment efficacy, and routine soluble-Pb assays. Industry can adapt by specifying composting or alternative treatments that demonstrably reduce F1 Pb and maintain higher Kd. Research gaps include treatment processes that disrupt CAlk–O/di-O linkages without harming agronomy. Practically, mandate litter testing, apply conservative rates, prefer aged materials with documented sorption performance, and verify crop Pb against HTMC benchmarks.
Citation
Souza CCBD, Lima ESA, García AC, Amaral Sobrinho NMB. (2024). Role of organic fertilizer in the transfer of lead to vegetables produced in tropical mountain agroecosystems. Archives of Environmental Contamination and Toxicology, 87, 446–459. doi.org/10.1007/s00244-024-01094-6
Lead is a neurotoxic heavy metal with no safe exposure level. It contaminates food, consumer goods and drinking water, causing cognitive deficits, birth defects and cardiovascular disease. HMTC’s rigorous lead testing applies ALARA principles to protect infants and consumers and to prepare brands for tightening regulations.
